Patent GB-528334-A (GB)
Title: Interlock for sewing machines
IPC: D05B65/00
Filed: 1939-05-04
Abstract: 528,334. Sewing-machines. FAIRWEATHER, W. C. (Singer Manufacturing Co.). May 4, 1939, No. 13324. [Class 112] Starting and stopping gear; button-attaching machines. In a machine with a work-clamp, operating in a predetermined cycle, means are provided to prevent the clamp from being lifted until the cycle has been so nearly completed that no damage to the work or the needle will result, while any premature attempt to lift the clamp will not interfere with the action of the stopgear ; the machine is also prevented from starting while the clamp is raised. A slide-bar adapted in one position to lock the clamp-lifting lever against actuation is moved to that position by the stop-gear when the machine is started and is held there, against biassing means, by a latch which prevents its return to the unlocking position, even after the stop-gear has been actuated to stop the machine, until it is actuated by the shaft in the final part of its last rotation. In the button-sewing machine shown, the main shaft 8 is belt driven through fast and loose pulleys 11, 13 respectively with a belt-shifting fork 41 carried on a member 31 which is slidably mounted at one end on a fixed pin 38 and is secured at the other end to a rod 33 sliding in bearings in the frame, a spring 52 acting on the rod 33 to move the member 31 to the stopping position. Fig. 2 shows the parts in the position they occupy just before stopping, the member 31 being in its stopping position, while Fig. 3 shows the running position. In the stopping position a buffer spring 44 carried by the member 31 lies in the path of an abutment 43 fixed to the hub of the fast pulley 11 to stop the shaft 8 in the required position (with the needle raised); rebound is limited by a member 65, with buffer spring, carried by a housing 64 pivoted at 40 to the member 31 and acted on by a spring 67 so that it is lifted by the abutment 43 in the last revolution of the shaft before stopping and then snaps back behind the abutment. The member 31 is moved to the running position by a treadleoperated crank 48 engaging a pin 50 on a lug 51 fixed to the rod 33, and is normally held in this position by a spring-pressed pivoted latch 54 engaging the lug 51 ; the latch is released, at the beginning of the final stitch of the group, by a pin 58 on a wheel driven from the shaft 8 engaging an arm 57 on the latch, and the spring 52 then moves the member 31 to the stopping position, the movement being cushioned by a washer 62 on a collar on the rod 33. The buttonclamp is pressed downwards by a spring-pressed plunger (not shown), and is raised by a chain attached to an arm on a rock-shaft running along the bracket-arm of the machine and carrying a second arm pivoted to a vertically-sliding rod 23 which is depressed, to open the clamp, by a treadle-operated chain against the action of a spring 24. The rod 23 has a notch in which engages a bar 68 sliding in the frame and pressed against a bracket 72 on the member 31 by a spring 70, the bar 68 having a notch 68a so that the rod 23 is free to move when the bar 68 has followed the member 31 to its stopping position, the bar 68 then being locked so that the machine cannot be started until the clamp is closed. In order to prevent release of the clamp immediately the stop mechanism is tripped, while the needle is still in the work, the bar 68 is held in the running position by a latch 73, Fig. 2, which is pressed upwards by a leaf-spring 81 to engage a notch 76 in the bar 68 ; this latch is released by the tail of the rebound-control housing 64 when the latter is raised by the abutment 43 immediately before stopping, and in order to prevent immediate relatching, in case the bar 68 is jammed by a premature attempt to release the clamp, the latch 73 is slidable on its pivot 71 under the action of a spring 79, which carries the latch longitudinally out of register with the notch 76. The stop mechanism is unaffected by the action of the interlocking devices, since the bar 68 only abuts against the member 31. Specification 463,533 is referred to.